Germany's foreign minister has called for continued investigation into the shadowy neo-Nazi terrorist group NSU, which killed nine immigrants between 2000 and 2007.
"It's a disgrace for us that the right-wing extremists could continue their killing spree for such a long time," Heiko Maas wrote on Twitter on Sunday, on the seventh anniversary of the exposure of the killers on November 4, 2011.
The Social Democrat politician admitted the mistakes by the police and intelligence, which had repeatedly ruled out a racist motive behind the murders, and instead treated migrant families as suspects.
"The investigations into this case must continue. It remains our duty to stand against far-right hatred anytime and anywhere," he stressed.
The National Socialist Underground (NSU) killed eight Turkish immigrants, one Greek citizen and a German police officer between 2000 and 2007, but the murders had long remained unresolved.
The German public first learned of the group's existence and its role in the murders in 2011, when two members -- Uwe Mundlos and Uwe Bohnhardt -- died after an unsuccessful bank robbery.
The group's only surviving member Beate Zschaepe was given a life sentence in July, but families of the victims expressed disappointment with the verdict and said the five-year-long trial has left many key questions unanswered.
Lawyers representing the families disputed the claim that the NSU was only an "isolated cell" of three far-right extremists, and demanded a deeper investigation into their possible ties to a wider network of far-right extremists in Germany.
Since the late 1990s, Germany's domestic intelligence agency, or BfV, recruited various informants from the right-wing who were believed to have had contacts with the trio.
Officials insisted they had no prior information about the existence of the NSU terror cell and its role behind the killings.
However, the central German state of Hesse's decision to keep several documents secret for 120 years, prompted further speculations about the NSU's possible ties.
